Chemistry:Aluminium isopropoxide

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Aluminium isopropoxide
One enantiomorph of Al4(OiPr)12
Names
IUPAC name
Aluminium Isopropoxide
Other names
Triisopropoxyaluminium
Aluminium isopropanolate
Aluminium sec-propanolate
Aluminium triisopropoxide
2-Propanol aluminium salt
AIP
Identifiers
3D model (JSmol)
ChemSpider
EC Number
  • 209-090-8
RTECS number
  • BD0975000
UNII
Properties
C9H21AlO3
Molar mass 204.246 g·mol−1
Appearance white solid
Density 1.035 g cm−3, solid
Melting point Sensitive to purity:
138–142 °C (99.99+%)
118 °C (98+%)[1]
Boiling point @10 Torr 135 °C (408 K)
Decomposes
Solubility in isopropanol Poor
Structure
monoclinic
Hazards
Main hazards Flammable (F)
GHS pictograms GHS02: Flammable
GHS Signal word Warning
H228
P210, P240, P241, P280
NFPA 704 (fire diamond)
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g. canola oilHealth code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformReactivity code 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g. white phosphorusSpecial hazards (white): no codeNFPA 704 four-colored diamond
1
2
2
Flash point 16 °C (61 °F; 289 K)
Related compounds
Other cations
 Titanium isopropoxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references
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Aluminium isopropoxide is the chemical compound usually described with the formula Al(O-i-Pr)3, where i-Pr is the isopropyl group (–CH(CH3)2). This colourless solid is a useful reagent in organic synthesis.[1]

Structure

A tetrameric structure of the crystalline material was verified by NMR spectroscopy and X-ray crystallography. The species is described by the formula Al[(μ-O-i-Pr)2Al(O-i-Pr)2]3.[2][3] The unique central Al is octahedral, and three other Al centers adopt tetrahedral geometry. The idealised point group symmetry is D3.

Preparation

This compound is commercially available. Industrially, it is prepared by the reaction between isopropyl alcohol and aluminium metal, or aluminium trichloride:

2 Al + 6 iPrOH → 2 Al(O-i-Pr)3 +3H2
AlCl3 + 3 iPrOH → Al(O-i-Pr)3 + 3 HCl

The procedure entails heating a mixture of aluminium, isopropyl alcohol, with a small amount of mercuric chloride. The process occurs via the formation of an amalgam of the aluminium. A catalytic amount of iodine is sometimes added to initiate the reaction.[4] The industrial route does not use mercury.[5]

Reactions

Aluminium isopropoxide is used in MPV reductions of ketones and aldehydes and the Oppenauer oxidation of secondary alcohols.[6] In these reactions, it is assumed that the tetrameric cluster disaggregates. It is used in the Tishchenko reaction.

MPV-reduction.png

Being a basic alkoxide, Al(O-i-Pr)3 has been also investigated as a catalyst for ring opening polymerization of cyclic esters.[7]

History

Aluminium isopropoxide was first reported in the master's thesis of the Russian organic chemist Vyacheslav Tishchenko (Вячеслав Евгеньевич Тищенко, 1861–1941), which was reprinted in the Journal of the Russian Physico-Chemical Society (Журнал Русского Физико-Химического Общества) of 1899.[8] This contribution included a detailed description of its synthesis, its peculiar physico-chemical behavior, and its catalytic activity in the Tishchenko reaction (catalytic transformation of aldehydes into esters). It was later found also to display catalytic activity as a reducing agent by Meerwein and Schmidt in the Meerwein–Ponndorf–Verley reduction ("MPV") in 1925.[9][10] The reverse of the MPV reaction, oxidation of an alcohol to a ketone, is termed the Oppenauer oxidation. The original Oppenauer oxidation employed aluminium butoxide in place of the isopropoxide.[11]

Related compounds

  • Aluminium phenolate
  • Aluminium tert-butoxide, which is a dimer [(t-Bu-O)2Al(μ-O-t-Bu)]2.[12] It is prepared analogously to the isopropoxide.[13]

References

  1. ↑ 1.0 1.1 Ishihara, K.; Yamamoto, H. (2001). "Aluminum Isopropoxide". Encyclopedia of Reagents for Organic Synthesis. John Wiley & Sons. doi:10.1002/047084289X.ra084. ISBN 0471936235. 
  2. ↑ Folting, K.; Streib, W. E.; Caulton, K. G.; Poncelet, O.; Hubert-Pfalzgraf, L. G. (1991). "Characterization of aluminum isopropoxide and aluminosiloxanes". Polyhedron 10 (14): 1639–46. doi:10.1016/S0277-5387(00)83775-4. 
  3. ↑ Turova, N. Y.; Kozunov, V. A.; Yanovskii, A. I.; Bokii, N. G.; Struchkov, Yu T.; Tarnopolskii, B. L. (1979). "Physico-chemical and structural investigation of aluminium isopropoxide." J. Inorg. Nucl. Chem. 41(1): 5-11, doi:10.1016/0022-1902(79)80384-X.
  4. ↑ Young, W.; Hartung, W.; Crossley, F. (1936). "Reduction of Aldehydes with Aluminum Isopropoxide". J. Am. Chem. Soc. 58: 100–102. doi:10.1021/ja01292a033. 
  5. ↑ Otto Helmboldt; L. Keith Hudson; Chanakya Misra; Karl Wefers; Wolfgang Heck; Hans Stark; Max Danner; Norbert Rösch. "Ullmann's Encyclopedia of Industrial Chemistry". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a01_527.pub2. 
  6. ↑ Eastham, Jerome F.; Teranishi, Roy (1955). "Δ4-Cholesten-3-one". Organic Syntheses 35: 39. doi:10.15227/orgsyn.035.0039. 
  7. ↑ Tian, D.; Dubois, Ph.; Jérôme, R. (1997). "Macromolecular Engineering of Polylactones and Polylactides. 22. Copolymerization of ε-Caprolactone and 1,4,8-Trioxaspiro[4.6]-9-undecanone Initiated by Aluminum Isopropoxide". Macromolecules 30 (9): 2575–2581. doi:10.1021/ma961567w. 
  8. ↑ Тищенко, B. E. (Tishchenko, V. E.) (1899). "Действие амальгамированного алюминия на алкоголь. Алкоголятов алюминия, их свойства и реакции" (in ru). Журнал Русского Физико-Химического Общества (Journal of the Russian Physico-Chemical Society) 31: 694–770. https://books.google.com/books?id=XGsMAQAAIAAJ&pg=PA694. 
  9. ↑ Meerwein, H.; Schmidt, R. (1925). "Ein neues Verfahren zur Reduktion von Aldehyden und Ketonen" (in de). Justus Liebigs Ann. Chem. 444: 221–238. doi:10.1002/jlac.19254440112. 
  10. ↑ Wilds, A. L. (1944). "Reduction with Aluminum Alkoxides (The Meerwein-Ponndorf-Verley Reduction)". Org. React. 2 (5): 178–223. doi:10.1002/0471264180.or002.05. 
  11. ↑ Oppenauer, R. V. (1937). "Eine Methode der Dehydrierung von Sekundären Alkoholen zu Ketonen. I. Zur Herstellung von Sterinketonen und Sexualhormonen" (in de). Recl. Trav. Chim. Pays-Bas 56 (2): 137–144. doi:10.1002/recl.19370560206. 
  12. ↑ Holleman, A. F.; Wiberg, E. (2001). Inorganic Chemistry. San Diego: Academic Press. ISBN 0-12-352651-5. 
  13. ↑ Wayne, Winston; Adkins, Homer (1941). "Aluminum tert-Butoxide". Organic Syntheses 21: 8. doi:10.15227/orgsyn.021.0008. 



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